The present invention relates to a speaker system, in particular to a speaker system for use in an automobile vehicle.
It has been known that a speaker system for use in an automobile vehicle is usually a multi-speaker system, such as that shown in FIG. 6.
Referring to FIG. 6, a conventional multi-speaker system comprises a plurality of speakers 4 disposed in a front section, side doors 2 and a rear tray 3 within an automobile vehicle 1. With the use of such an arrangement, it is possible for an entire area within the vehicle to obtain a uniform sound pressure, enabling all the persons staying in the vehicle to easily and similarly enjoy music or the like.
However, there is a problem with the conventional multi-speaker system illustrated in FIG. 6. Namely, in use of the speaker system, there are primary sounds emitted directly from individual speakers 4 and secondary sounds generated when the primary sounds are reflected from inner wall of the automobile vehicle. Since the primary sounds and the secondary sounds will be unavoidably synthesized together, there is always a fluctuation in the frequency characteristic of the multi-speaker system (due to a reflection synthesizing effect), resulting in a complex peak/dip phenomenon in audible frequency bands.
To alleviate the problem caused by the reflection synthesizing effect, it is necessary to simplify the sound sources involved in a multi-speaker system. Namely, the number of speakers (serving as sound sources) should be made as fewer as possible and these speakers should be arranged in only one direction. Further, to ensure an audio effect similar to a music listening room, it is important to satisfy the following requirements.
(a) A sound image should be located in the front. PA1 (b) A sound image deviation caused due to different seat positions within an automobile vehicle should be eliminated. PA1 (c) A peak/dip phenomenon caused due to the reflection synthesizing effect should be eliminated.
In the above three requirements, requirement (a) is particularly important for obtaining a satisfactory effect of music enjoyment. That is, if a person wants to fully enjoy music, the music sound image should be located in the front, so that music sound could come from the front, making it easy for a person to naturally hear and fully enjoy the music. This fact may also be understood in view of the structure of a man's ears.
However, in the multi-speaker system shown in FIG. 6, since the speakers are disposed in every direction for the purpose of creating a uniform music space within an automobile vehicle, it is difficult to have the sound image located in the front within a vehicle. In detail, since there are speakers 4 disposed in the front section, on the side doors 2 and on the rear tray 3 within the vehicle 1, sound signals reflected from inner walls of the vehicle 1 will reach person's ears much later than the sound signals directly emitted from the speakers. As a result, it is impossible to have a sound image located in the front within the vehicle 1. Particularly, in the multi-speaker system shown in FIG. 6, a sound image will be unavoidably located behind a driver and a passenger sitting beside the driver. Consequently, the driver and the passenger will have uncomfortable sound feelings, making it difficult for them to fully enjoy music.